Insulation diagnostic system and insulation diagnostic method

Abstract

According to one embodiment, an insulation diagnostic system comprising: a peak-value acquisition circuit configured to acquire at least one peak value of a section corresponding to local discharge of a voltage signal acquired by at least one sensor that detects the voltage signal in a non-contact manner; a function acquisition circuit configured to acquire a calculation function for calculating charge amount related to the discharge based on at least two peak values acquired from the voltage signal that is detected by the sensor by applying a test voltage to a rotating electrical machine while the rotating electrical machine is stopped; and a charge-amount calculation circuit configured to calculate the charge amount related to partial discharge of the rotating electrical machine based on the calculation function and the peak value obtained from the voltage signal that is detected by the sensor during operation of the rotating electrical machine.

What is claimed is: 
     
       1. An insulation diagnostic system comprising:
 a peak-value acquisition circuit configured to acquire at least one peak value of a section corresponding to local discharge of a voltage signal acquired by at least one sensor that detects the voltage signal in a non-contact manner, the voltage signal being a signal propagating through a conductor connected to a rotating electrical machine; 
 a function acquisition circuit configured to acquire a calculation function for calculating charge amount related to the discharge based on at least two peak values acquired from the voltage signal that is detected by the sensor by applying a test voltage to the rotating electrical machine while the rotating electrical machine is stopped; and 
 a charge-amount calculation circuit configured to calculate the charge amount related to partial discharge of the rotating electrical machine based on the calculation function and the peak value obtained from the voltage signal that is detected by the sensor during operation of the rotating electrical machine. 
 
     
     
       2. The insulation diagnostic system according to  claim 1 , wherein the peak value is a value at which an absolute value is maximized. 
     
     
       3. The insulation diagnostic system according to  claim 1 , wherein:
 the function acquisition circuit is configured to:
 acquire at least two test data indicating relationship between a known charge amount and a known peak value when the test voltage is applied to the rotating electrical machine, and 
 acquire the calculation function from a graph of an approximate curve obtained from the at least two test data; and 
 
 the charge-amount calculation circuit is configured to calculate an unknown charge amount from a newly acquired peak value based on the calculation function. 
 
     
     
       4. The insulation diagnostic system according to  claim 1 , further comprising:
 a database configured to store residual-life information indicating relationship between the charge amount and residual life of the rotating electrical machine; and 
 a residual-life calculation circuit configured to calculate the residual life of the rotating electrical machine from the charge amount related to the partial discharge and the residual-life information stored in the database. 
 
     
     
       5. The insulation diagnostic system according to  claim 4 , wherein the residual-life calculation circuit is configured to:
 estimate an electrical breakdown characteristic of the rotating electrical machine by associating first characteristic data with second characteristic data, the first characteristic data indicating a characteristic of the charge amount related to the partial discharge, the second characteristic data indicating a characteristic of a period of use acquired from the rotating electrical machine in a current state; and 
 calculate time length required for the charge amount related to the partial discharge to reach a preset characteristic threshold, as the residual life, based on the electrical breakdown characteristic. 
 
     
     
       6. The insulation diagnostic system according to  claim 4 , wherein:
 the database is configured to store information on the charge amount and a progression function of a progression rate of an electrical breakdown path; and 
 the residual-life calculation circuit is configured to calculate the residual life by executing first processing and second processing,
 the first processing being processing of calculating a first progression distance of the electrical breakdown path by time-integrating the progression rate calculated from the progression function and the information on the charge amount, 
 the second processing being processing of calculating a second progression distance of the electrical breakdown path by a tool that models progression of the electrical breakdown path by numerical calculation. 
 
 
     
     
       7. The insulation diagnostic system according to  claim 6 , wherein an acceptable threshold error at a time of calculating the residual life is set based on a value obtained by dividing an absolute value of difference between the first progression distance and the second progression distance by the first progression distance. 
     
     
       8. The insulation diagnostic system according to  claim 1 , wherein, when a reference voltage equal to or higher than a preset trigger voltage is detected by the sensor, at least one specific period before and after detection of the reference voltage is set as the section. 
     
     
       9. An insulation diagnostic system comprising:
 a spectrum acquisition circuit configured to acquire a spectrum of a section corresponding to local discharge of a voltage signal obtained by at least one sensor that detects the voltage signal in a non-contact manner, the voltage signal being a signal propagating through a conductor connected to a rotating electrical machine; 
 a coefficient acquisition circuit configured to acquire a conversion coefficient represented by a ratio between two spectra corresponding to respective two points obtained from the voltage signal that is detected by the sensor by applying a test voltage to the two points while the rotating electrical machine is stopped, the two points including a point of a measurement target of the rotating electrical machine and a point of the sensor; 
 a waveform restoration circuit configured to restore a time waveform of the voltage signal at an occurrence time of partial discharge at the point of the measurement target, based on the conversion coefficient and the spectrum obtained from the voltage signal detected by the sensor during operation of the rotating electrical machine; and 
 a charge-amount calculation circuit configured to calculate charge amount related to the partial discharge from the time waveform. 
 
     
     
       10. The insulation diagnostic system according to  claim 9 , wherein the charge-amount calculation circuit is configured to offset the time waveform. 
     
     
       11. The insulation diagnostic system according to  claim 9 , wherein the charge-amount calculation circuit is configured to:
 calculate a specific value (MK) by multiplying a maximum value (M) among absolute values in the time waveform by a specific coefficient (K); and 
 calculate the charge amount from a first range and a second range in the time waveform, the first range being a range in which each value is a negative specific value (−MK) or lower, the second range being a range in which each value is a positive specific value (+MK) or higher. 
 
     
     
       12. The insulation diagnostic system according to  claim 9 , wherein the charge-amount calculation circuit is configured to:
 extract digital data in a range from a maximum value when absolute values of the time waveform are arranged in descending order to a preset specific point; and 
 calculate the charge amount from the digital data. 
 
     
     
       13. The insulation diagnostic system according to  claim 9 , wherein the charge-amount calculation circuit is configured to calculate the charge amount based on a quotient that is obtained by dividing a sum of products of absolute values of the time waveform and time derivative by an impedance value of detection impedance. 
     
     
       14. An insulation diagnostic method comprising steps of:
 acquiring at least one peak value of a section corresponding to local discharge of a voltage signal acquired by at least one sensor that detects the voltage signal in a non-contact manner, the voltage signal being a signal propagating through a conductor connected to a rotating electrical machine; 
 acquiring a calculation function for calculating charge amount related to the discharge based on at least two peak values acquired from the voltage signal that is detected by the sensor by applying a test voltage to the rotating electrical machine while the rotating electrical machine is stopped; and 
 calculating the charge amount related to partial discharge of the rotating electrical machine based on the calculation function and the peak value obtained from the voltage signal that is detected by the sensor during operation of the rotating electrical machine. 
 
     
     
       15. An insulation diagnostic method comprising steps of:
 acquiring a spectrum of a section corresponding to local discharge of a voltage signal obtained by at least one sensor that detects the voltage signal in a non-contact manner, the voltage signal being a signal propagating through a conductor connected to a rotating electrical machine; 
 acquiring a conversion coefficient represented by a ratio between two spectra corresponding to respective two points obtained from the voltage signal that is detected by the sensor by applying a test voltage to the two points while the rotating electrical machine is stopped, the two points including a point of a measurement target of the rotating electrical machine and a point of the sensor; 
 restoring a time waveform of the voltage signal at an occurrence time of partial discharge at the point of the measurement target, based on the conversion coefficient and the spectrum obtained from the voltage signal detected by the sensor during operation of the rotating electrical machine; and 
 calculating charge amount related to the partial discharge from the time waveform.